Originally posted by Shiki Hiya, I'm new here. I was wondering which encoder and what settings I should use to create a MPEG-4 compliant AAC that I can mux with my video to be able to play on (future) standalone players?

You can use Psytel AACenc. I would suggest creating an AAC LC with ADTS header. If the multiplexer outputs some error because of the header, try creating a RAW AAC LC (switch -nh )

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Will there be much difference if I transcode a DVD AC3 file into AAC? What should I do to minimise the quality loss? Can AAC do 5.1 channel sound?

Yes. Psytel AACenc creates 5.1 AAC file, and you can use the -lfe switch to create the LFE channel.

I don't know about transcoding. Usually is bad but, if you want to shrink the bitrate of the stream, itīs much better than using AC3 for this purpose. (Even Dolby agrees that AAC is superior to AC3 altough, according to Ivan, they "play with the words")

Regards;

Roberto.

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Get up-to-date binaries of Lame, AAC, Vorbis and much more at RareWares:http://www.rarewares.org

Originally posted by macdaddy Does this mean that XviD/.ac3 will be supported by the ISO/standalone players?

XviD IS MPEG4 video simple profile. No more. You can rename it to DivX, or multiplex in a MP4 file, and it will work fine.

Regarding AC3 (Or any other format: OGG, MPC...), I don't think so, and I don't hope so. I don't think so, because AC3 is not part of MPEG4 standard. And I don't hope so because AAC is better than AC3.

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Get up-to-date binaries of Lame, AAC, Vorbis and much more at RareWares:http://www.rarewares.org

I don't think so, because AC3 is not part of MPEG4 standard. And I don't hope so because AAC is better than AC3.

How so? I hope you know me well enough to know I am not being antagonistic, merely inquisitive. rjamorim, you seem to be a big proponent of the .aac format, and I am curious as to the specific reasons why. Thanks for the indulgence...

Up to this point, I thought that leavng .ac3 audio alone was the way to go. Does ISO MPEG-4 have a specified audio format, like SVCD(mpeg-2) format has .mp2? Does MPEG-4 only apply to the video? If it applies to audio (and .ac3 is out, and .aac is in) what about the .mpc and .ogg audio formats? When products (like sigma's xcard) say MPEG-4 compliant, is there only one audio/video format that works, or are these products simply processing the video (the MPEG-4 part) and passing through the audio to the soundcard?

Originally posted by macdaddy Up to this point, I thought that leavng .ac3 audio alone was the way to go.

This is true.

I think rjamorim was referring to AAC as being better than AC3 when encoding from the same source material, not in terms of transcoding. But I have never made a direct comparison between AC3 and AAC so I also await rjamorim's response

How so? I hope you know me well enough to know I am not being antagonistic, merely inquisitive. rjamorim, you seem to be a big proponent of the .aac format, and I am curious as to the specific reasons why. Thanks for the indulgence...

Regarding AAC being better than AC3, I trust Ivan's words in this matter. You can see his post here, around the middle of the thread.

Regarding why I prefer AAC rather than Musepack or Vorbis:

1. - It's an ISO standard, and the MPEG4 official audio format. So, if, in the future, I decide to multiplex the audio in a MP4 strem, It'll be piece of cake.

2. - The quality is great at the bitrates I use (160 - 200). I don't need more than that for the kinds of music I enjoy.

3. - It already has Hardware support, and I keep dreaming on buying an Expanium someday.

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Up to this point, I thought that leavng .ac3 audio alone was the way to go. Does ISO MPEG-4 have a specified audio format, like SVCD(mpeg-2) format has .mp2?

Does MPEG-4 only apply to the video? If it applies to audio (and .ac3 is out, and .aac is in) what about the .mpc and .ogg audio formats? When products (like sigma's xcard) say MPEG-4 compliant, is there only one audio/video format that works, or are these products simply processing the video (the MPEG-4 part) and passing through the audio to the soundcard?

I would have to take a look at the card specs, but I would bet that it focuses in video decoding, and the audio decoding is mainly (If not completely) processed by the CPU.

As example, there's the case of DVD hardware accelerators. The main tasks they perform are iDCT (which provides about 40% decoding acceleration) and Motion Compensation (30% decoding acceleration). Most of the audio decoding (AC3, DTS...) is performed by the CPU, as well as 30% of the video decoding.

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I apologize for my ignorance; thanks for any input.

No problem.

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Originally posted by Tes

I think rjamorim was referring to AAC as being better than AC3 when encoding from the same source material, not in terms of transcoding. But I have never made a direct comparison between AC3 and AAC so I also await rjamorim's response

That's It.
And I mentioned something like that, when said that, to reduce the size of an 5.1 audio stream, it would be better to transcode to 5.1 AAC than to reencode in AC3 in a lower bitrate.

Regards;

Roberto.

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Get up-to-date binaries of Lame, AAC, Vorbis and much more at RareWares:http://www.rarewares.org

Thanks for clarifying-I will read the referenced thread when I get home from work...

Hopefully with the xcard, like with current h+, the .ac3 will pass through to the receiver, not requiring any processing at all. I am assuming that .aac cannot be passed through in this way-I don't think the surround receiver will not recognize 5.1 .aac audio (in which case the audio woould have to e processed by CPU)...

I am asking because I am starting to put together MPEG-4 clips to test on the new card when it arrives (after being shipped at the end if this month)...

I don't think the Xcard will handle 5.1 AAC audio. If you look at the MPEG-4 chip used, it is supposed to support profile Level 2 MPEG-4 audio which can only handle 2-channels I believe. Maybe some other company will design an MPEG-4 chip in the future that can handle 5.1 AAC...